PRIORITY CLAIM
TECHNICAL FIELD
[0002] A field of the invention is microplasma devices and arrays, and metal and metal oxide-based
microplasma devices and arrays, in particular. Devices and arrays of the invention
have many applications, including, for example, displays and the plasma treatment
processing of gases and liquids. Specific example applications include air and water
purification, ozone production, the plasmachemical conversion of CO
2 into industrially-valuable feedstock gases, and the filtering of air.
BACKGROUND ART
[0003] Microplasma devices developed by the present inventors have been formed in various
materials and configurations. Such devices are capable of igniting and sustaining
glow discharges in microcavities having a characteristic dimension between approximately
5 µm and 500 µm. Electrodes are generally designed to ignite a plasma within each
microcavity. Designs for the electrodes differ but most are azimuthally symmetric
with respect to one or all cavity apertures. Prior arrays developed by the present
inventors and colleagues have many applications, such as displays, lighting, as well
as the production of ozone for water treatment.
[0004] For example,
Park et al, U.S. Published Application Number 20100296978 discloses microchannel lasers having a microplasma gain medium. In that application,
microplasma acts as a gain medium with the electrodes sustaining the plasma in the
microchannel. Reflectors can be used in conjunction with the microchannel for obtaining
optical feedback and lasing in the microplasma medium in devices of the invention
for a wide range of atomic and molecular species. Several atomic and molecular gain
media will produce sufficiently high gain coefficients that reflectors (mirrors) are
not necessary. FIG. 4 of that application also discloses a microchemical reactor that
is suitable for air purification and ozone production because of the channel lengths
and large plasma power loadings (watts deposited per unit volume) that are available.
However, fabrication costs associated with channels of extended length present an
obstacle to commercialization for this technology for many applications that would
benefit from ozone production.
[0005] Ozone is the strongest oxidant and disinfectant available commercially. Mechanisms
of disinfection using ozone include direct oxidation/destruction of bacterial cell
walls, reactions with radical by-products of ozone decomposition, and damage to the
constituents of nucleic acids. Presently available commercial devices for the large
scale production of ozone are generally expensive devices having high power requirements.
Ozone is produced when oxygen (O
2) molecules are dissociated by an energy source into oxygen atoms. Collisions with
oxygen molecules produce ozone (O
3), which must be generated at the point of treatment because the lifetime of O
3 in air at atmospheric pressure is in the order of minutes. Commercial ozone generators
having sufficient capacity for municipal water treatment, for example, are large (as
much as 10-15 ft. in length) and have demanding power requirements (150-200 kVA).
Furthermore, the conversion of feedstock gases into O
3 is typically inefficient. Existing commercial processes for producing O
3 in large volume typically convert 15% - 18% of the oxygen (O
2) feedstock gas into O
3. Maintenance of such system is also problematic owing to a large number of ceramic
parts and fouling of device components by nitric acid. Inexpensive and compact devices
for high-efficiency generation of ozone would have many important applications.
DISCLOSURE OF INVENTION
[0007] The invention is defined by the claims. An embodiment of the invention is an array
of microtip microplasma devices in which each microtip microplasma device has a first
metal microtip opposing a second metal microtip with a gap therebetween. The first
and second metal microtips are encapsulated in metal oxide that electrically isolates
and physically connects the first and second metal microtips. In preferred devices,
the first and second metal microtips and metal oxide comprise a monolithic, unitary
structure. In an array, the first metal microtip is a portion of a first electrode
and the second metal microtip a portion of a second electrode, with the first and
second electrodes and said metal oxide defining a mesh with microscale openings therein.
Arrays can be flexible, can be arranged in stacks, or formed into cylinders, for example,
for gas and liquid processing devices, air filters and other applications.
[0008] A preferred method of forming an array of microtip microplasma devices provides a
metal mesh with an array of micro openings therein. Electrode areas of the metal mesh
are masked, leaving planned connecting metal oxide areas of the metal mesh unmasked.
Planned connecting metal oxide areas are electrochemically etched to convert the planned
connecting metal oxide areas to metal oxide that encapsulates opposing metal microtips
therein. The mask is removed. The electrode areas are electrochemically etched to
encapsulate the electrode areas in metal oxide.
BRIEF DESCRIPTION OF DRAWINGS
[0009]
FIG. 1A is a schematic cross-section diagram of a portion of an array of microtip
plasma devices of the invention mounted on a substrate;
FIG 1B is a photograph of a portion of an array of opposing microtips of the invention,
showing a pair of microtips in an array of the invention formed from aluminum mesh
and encapsulated in Al2O3;
FIGs. 2A-2H illustrate a preferred method of the invention for fabricating arrays
of opposed microtips mounted onto a porous substrate;
FIGs. 3A-3C illustrate in plan view a preferred method for forming arrays of microtip
plasma devices of the invention encapsulated in a metal oxide;
FIGs. 4A-4D are photographs showing four stages in the formation of opposing microtips
from an aluminum mesh;
FIG. 5 is a graph of the dependence of current density on etching time for the anodization
process (Step VI) of FIG 2. The inset to the figure presents a magnified view of the
data at the point (shown by the dashed circle) at which an aluminum link in a mesh
is chemically severed and a microtip pair is formed;
FIGs. 6A-6A is a sequence of diagrams illustrating a preferred embodiment method of
the invention for forming arrays of microtip pairs of the invention;
FIG. 7 is a microphotograph of a portion of an array of microtip plasma devices of
the invention producing microplasmas in neon gas;
FIG. 8 is a diagram of an array of microtip plasmas devices of the invention rolled
into the form of a cylinder for the purpose of converting air or O2 into ozone (O3);
FIG. 9 illustrates a preferred device of the invention that purifies air by destroying
biological and chemical pollutants with ozone generated by microtip plasma devices
of the invention;
FIG. 10 illustrates another preferred device of the invention having arrays of microtip
plasma devices of the invention that are rolled in the form of a scroll for the purpose
of chemically altering one or more input gases so as to produce a product of industrial
value; and
FIG. 11 is a schematic cross-section device of the invention for the purification
of water with ultraviolet light generated by a microtip plasma array of the invention
immersed in a gas or mixture of gases.
BEST MODE OF CARRYING OUT THE INVENTION
[0010] An embodiment of the invention is a microtip microplasma device having a first metal
microtip opposing a second metal microtip with a gap therebetween. The first and second
metal microtips are encapsulated in metal oxide that electrically isolates and physically
connects the first and second metal microtips. In preferred devices, the first and
second metal microtips and metal oxide comprise a monolithic, unitary structure. Arrays
of the microtip microplasma devices can be formed. In an array, the first metal microtip
can be a portion of a first electrode and the second metal microtip a portion of a
second electrode, with the first and second electrodes and said metal oxide defining
a mesh with microscale openings therein. Arrays can be flexible, can be arranged in
stacks, or can be formed into cylinders, for example, for gas and liquid processing
devices, air filters and other applications.
[0011] Embodiments of the invention include arrays of microtip plasma devices formed from
opposing microtips encapsulated in dielectric, where each pair of microtips is capable
of producing plasma in a gas or mixture of gases lying immediately adjacent to the
encapsulating dielectric and in the vicinity of a microtip pair. Such an array of
microplasmas can generate ultraviolet (UV) or vacuum ultraviolet (VUV) radiation capable
of, for example, destroying pathogens in water and thus improving the purity of water
in a municipal supply. Other applications for the microplasmas generated by microtips
of the invention include the plasmachemical conversion of greenhouse gases or atmospheric
pollutants into industrial feedstock gases or liquids.
[0012] A preferred method of forming an array of microtip microplasma devices provides a
metal mesh with an array of micro(or mm-scale) openings therein. Electrode areas of
the metal mesh are masked, leaving planned connecting metal oxide areas of the metal
mesh unmasked. Planned connecting metal oxide areas are electrochemically etched to
convert metal in these specific areas to metal oxide that physically connects and
encapsulates opposing metal microtips therein. The mask is removed. The electrode
areas are electrochemically etched to encapsulate the electrode areas in metal oxide.
The dielectric gaps and encapsulated microtips have cross-sectional dimensions smaller
than, but comparable to those of original mesh, but each opposing set of tips supports
the generation and sustenance of intense plasma that can encircle each dielectric
gap and microtip pair if space is left above and below the array.
[0013] Preferred embodiments of the invention will now be discussed with respect to the
drawings. The drawings may include schematic representations, which will be understood
by artisans in view of the general knowledge in the art and the description that follows.
Features may be exaggerated in the drawings for emphasis, and features may not be
to scale. The preferred embodiments are discussed with respect to experiments that
were conducted with an aluminum and aluminum oxide based fabrication method. Another
example system is titanium and titanium oxide.
[0014] FIGs. 1A and 1B illustrate preferred embodiment arrays of microtip plasma devices
of the invention. FIG. 1A is schematic side view of an array mounted on a substrate
6 with an adhesive layer 10, and FIG. 1B is a photograph of an experimental array.
The photograph of FIG. 1B was recorded by a CCD camera (coupled with a telescope)
of a portion of an array of oxide-encapsulated microtip plasma devices of the invention
fabricated from a metal mesh, such as an aluminum mesh.
[0015] The array shown in FIGs. 1A and FIG. 1B include a plurality opposing a microtip pair
12a, 12b in a preferred embodiment microtip plasma array. The pair 12a, 12b is encapsulated
by dielectric 14 that also fills/occupies a gap 16 that electrically separates the
opposing pair while mechanically joining the pair 12a, 12b. Each tip has a respective
electrode 18a, 18b that is shared by other microtip plasma devices in the array. The
electrodes 18a, 18b are also coated with dielectric 14 to protect them from sputtering.
The array in FIG. 1 is readily formed from a wire mesh that defines openings/cavities
20 that, with the dielectric 14 that occupies the gaps 16 serves to isolate the electrodes
18a, 18b from each other. The electrodes 18a and 18b continue in the vertical direction
in FIG. 1A to provide the necessary alternating voltage for a plurality of the microtip
pairs in the array, each of which ignites and sustains and intense plasma that surrounds
each pair of microtips and associated dielectric gap.
[0016] The array of microtips can be mounted onto the substrate 8 with an adhesive layer
6 as shown in FIG. 1A, which can be any of a variety of materials including polymers
or glass frit. Alternatively, arrays can operate without attachment to a substrate,
and even in standard atmosphere as a result of intense electric fields that can be
produced. The substrate 6 can preferably be porous, having a pattern of holes extending
through the substrate to allow for the passage of a gas or liquid through the substrate.
Each microtip pair 12a, 12b is excited electrically through the electrodes 18a, 18b
by a time-varying (sinusoidal, RF, pulsed, etc.) voltage applied by the voltage source
22. The strong electric field produced in the region between the tips 12a, 12b and
in the region outside the metal oxide that connects and covers the tips will produce
a microplasma in this region if the peak value of the driving voltage is sufficiently
high and a gas is present.
[0017] As demonstrated in experiments, microtips 12a, 12b are formed and are shaped electrochemically
from the metal that constituted the original metal mesh. The mesh can be fabricated
from a metal sheet or can be obtained from a commercial source. Such meshes are available
in a wide variety of thicknesses and patterns having different geometries of openings
20, and such a commercial aluminum mesh was used to fabricate the array that is shown
in FIG. 1B. The microtip pair 12a, 12b of FIG 1B is separated by a specified and well-controlled
distance. Both metal microtips 12a, 12b are encapsulated in metal oxide 14 that electrically
isolates and physically connects the first and second metal microtips 12a, 12b. They
form part of a larger unitary, monolithic structure that is a larger array with the
electrodes 18a, 18b and dielectric 14 physically forming the unitary, monolithic structure.
The opposing microtips 12a and 12b, as well as the entire array, are formed by converting
metal, e.g., aluminum, into metal oxide, e.g., aluminum oxide on a spatially selective
basis. As a result, the two tips 12a, 12b are completely encapsulated in metal oxide,
which also forms a physical link portion that retains the original external shape
of a wire mesh that was used to form the array.
[0018] Experimental microtip microplasma devices and arrays of the invention include pairs
of aluminum microtips separated by a specified and well-controlled distance with typical
values of tens to several hundred µm. The tips 12a, 12b are formed within the connecting
links of which an aluminum mesh is composed. When the microtip pairs are formed, they
are simultaneously encapsulated in nanoporous aluminum oxide (alumina). Applying a
time-varying voltage to the metal mesh via a voltage source 22 (FIG. 1A) results in
the generation of an array of small glow discharges produced above (indeed, around)
the gap between each microtip pair but in the gas surrounding the mesh.
[0019] Experiments demonstrated inexpensive arrays of microplasma-generating electrode pairs
with the microtip structure, allowing for the electric field strength at which the
plasma is generated to be readily increased up to the breakdown strength of nanoporous
alumina while simultaneously allowing for the openness or transparency of the mesh
to be large. The intense electric fields achievable with microtips make arrays of
microtip pairs well-suited for generating microplasmas in attaching gases and other
gases (such as CO
2) that are difficult to dissociate (fragment) efficiently. Large, two dimensional
arrays can be formed. Each microtip is separated from its opposing partner by a fixed
distance (typically in the range of 10-700 µm) and all of the aluminum (from which
the microtips are formed), or just the microtips themselves, are encapsulated by a
dielectric layer such as alumina (Al
2O
3).
[0020] FIGs. 2A-2H is a sequence of cross-sectional diagrams that shows a preferred method
for forming the microtip arrays of FIGs. 1A and 1B. The process begins (FIG. 2A) with
a substrate 6 that can be porous in the sense that holes or slots (not shown in FIG.
2A) are provided that will allow a gas or liquid to pass through the substrate 6 in
the direction that is normal to the surface of the substrate. The substrate 6 is nonporous
in other embodiments. In FIG. 2B, a metal mesh 30, such as an aluminum mesh is affixed
to the substrate 6 via adhesive 8. The metal mesh 30 has a regular pattern of metal
links or interconnects with openings therebetween. The mesh can have a uniform or
variable thickness, the latter of which is shown in FIG. 2 The adhesive 8 can be,
for example, a polymer if the substrate 6 is also a polymer whereas if the substrate
is glass or ceramic, the optimal adhesive may be a glass frit. Once the mesh 30 is
mounted onto the substrate 6, anodizing the exposed metal, e.g., Al mesh by wet chemical
processing in, for example, oxalic acid produce a thin encapsulating layer of alumina
(Al
2O
3) 14 as shown in FIG. 2C. A typical thickness for this initial encapsulation layer
is ∼1 µm. In FIG. 2D, the entire mesh is coated with photoresist 31 and the selective
removal of photoresist 33 in FIG. 2E by photolithography to form a mask 34 by the
includes exposed areas of the mesh 30 having a length
d, which distance sets the desired gap between the microtips that will be formed. Also,
the areas selected for removal of the photoresist are generally those in which dielectric
linkage (14 in FIG. 1B) in the mesh pattern will lie. FIGs. 2F and 2G illustrate alternatives.
In FIG. 2F, the next process entails partially or fully converting the metal, having
the length
d, into metal oxide (e.g., Al
2O
3) 14. Subsequently (FIG. 2H), the photoresist mask 34 is removed and continued anodization
of the now entirely-exposed structure culminates in the formation of the microtips
12a and 12b and the encapsulation of all metal, e.g., Al in metal oxide, Al
2O
3.
[0021] The alternative route of FIG. 2G is to first etch the exposed Al links to form the
microtips 12a, 12b, and subsequently, remove the photoresist. The process sequence,
in either case as illustrated in FIG. 2H and would be subsequent to FIG. 2G, concludes
with on or both of anodizing the Al microtip pair array to complete dielectric formation
or by coating the array with a dielectric other than Al
2O
3. The latter can be accomplished by any of a variety of well-known techniques such
as evaporation or sputtering. The formed array can also be removed from the substrate
6 by dissolution or another method for remove the adhesive 8.
[0022] FIG. 3 illustrates a method of formation. For simplicity and clarity of presentation,
the metal structure (mesh or patterned foil) is shown without the oxide that encases
it and "links" the metal microtips. In FIG. 3A, the process begins with a mesh or
patterned foil 30 having links 38 between electrodes 32. As discussed earlier, a substrate
provides mechanical support to the metal mesh but the mesh need not, for several applications
of this invention, be permanently attached to the substrate. FIG. 3B illustrates the
application of photoresist 34 to the mesh in a pattern determined by the appropriate
mask pattern. Subsequent chemical processing (etching and/or anodization) of the mesh
produces (FIG. 3C) pairs of microtips 12a, 12b and two electrodes 18a, 18b. One microtip
for each pair in the array is electrically and physically connected to one of the
two electrodes (first electrode) while the other microtip in each pair is connected
to the second electrode. An attractive aspect of the fabrication sequence is that
only one photolithographic step is required to form the mask and the necessary spatial
resolution is quite low compared to the size of the tips that results, thus reducing
the cost for the fabrication process. In addition, the degree of etching (i.e. length
of time devoted to FIG. 2G or 2H) controls the gap between the tips and determines
the tip profile (as does the cross-section of the mesh that is initially used to form
the array).
[0023] The control with which the microtip shape (profile) and the gap between the microtips
can be specified is extraordinary. FIG. 4 is a sequence of four microphotographs showing
the transformation of portions of an Al mesh into Al
2O
3, forming microtips in the process of FIG. 2H. In FIG. 4A, the process of the tip
formation has just begun as only ∼25% of the width of Al link has been converted into
Al2O3. The arrow in FIG. 4A identifies one of the links at which the conversion process
is underway. In FIG. 4B, the process is more than 50% complete and, in FIG. 4C, the
growth of Al
2O
3 is on the verge of severing the Al link. Continuing to convert Al into Al
2O
3 (FIG 4D) widens the gap between the newly-formed microtips to ∼ 230 µm.
[0024] Tests show that the reproducible formation of microtip pairs having a specific profile
and gap can be accomplished by monitoring current flow during the anodization process
(FIG. 2G or 2H). Because the mesh structure serves as an electrode during anodization,
the current can be recorded throughout the process, as shown by the representative
trace in FIG. 5. At the point when the Al links are severe, the current drops precipitously
(see also the inset to FIG. 5). Consequently, recording the current during anodization
eliminates the need for periodically removing the mesh from the anodization bath and
visually determining the progress of the Al-to-Al
2O
3 conversion process. Continuing the anodization process a predetermined amount of
time beyond the "break point" of FIG. 5 results in an array of microtips having gaps
that are virtually constant over the entire array. In other words, the rate of increase
of the microtip gaps (beyond the breakpoint) was calibrated for specific anodization
bath concentrations and temperatures. In this way, the microtip pair gap and profile
can be controlled precisely.
[0025] FIGs. 6A-6I illustrate another embodiment method for forming arrays of the invention
that avoids a photolithographic step. The process begins (FIG. 6A) with metal, e.g.,
Al mesh 40, or a patterned foil that is anodized so as to encapsulate the mesh with
a layer of nanoporous Al
2O
3 (FIGs. 6B and 6C). In FIGs. 6D and 6E, the anodized mesh is affixed to a support
pad or substrate 44 having openings 46 (through holes or slots) that are partially
or fully aligned with portions of the mesh. With an ablation process such as micro-
or nano-powder blasting in FIGs. 6F and 6G, a portion of the "links" in the mesh are
removed to form gaps 48, after which anodization as described in FIGs. 2 and 3 will
form opposing, encapsulated microtips 50a, 50b in FIGs. 6H and 6I.
[0026] For arrays of the invention, the electrodes and interconnects are sealed or encapsulated
in nanoporous metal oxide. Advantageously, arrays can be produced from a single sheet
of commercially-available metal mesh with a fabrication procedure that requires only
one photolithographic step (or, as shown in FIG. 6, not at all). The entire electrical
structure, including the microgaps, is encapsulated, making these arrays extremely
robust. Microplasmas are formed outside, but immediately above and behind, the microgaps
in the gas in which the array is immersed due to the intense electric field. The electric
filed strength in each microgap is readily controlled by varying gap length and tests
show that arrays of microtip pairs operate well in the most challenging gases, including
air. It should also be noted that this design does not require microplasma to be formed
in the openings/microcavities in the mesh.
[0027] FIG. 7 is a microphotograph of a portion of an array of microplasmas produced when
an array of microtip pairs is immersed in 400 Torr of Ne and a 20 kHz, 283 V RMS sinusoidal
voltage is applied to the two electrodes as illustrated in FIGs 1A and 3C. Applying
a voltage to the electrodes generates an intense electric field between the two tips
of every gap in the array. The strength of this electric field is greatest in the
region between the tips but because this region is filled with metal oxide, a discharge
does not occur there. Instead, plasma is produced around the outside of the oxide
"links" that fill the microgaps between microtips.
[0028] FIGs. 8-11 illustrate several representative applications of the microtip arrays.
If the substrate of FIG.2 is removed after processing or, alternatively the substrate
is thin and flexible, then the array can be formed into a cylinder or several concentric
cylinders. As shown in FIG. 8, such a structure can be used to convert air or O
2 into ozone. In FIG. 8, multiple microtip arrays 62, 64 and 66 are enclosed in a vessel
68. A gas flow 70 including oxygen is through the vessel 68 and ozone 72 is created
by the strong plasmas generated around microtips in the arrays and exits the vessel.
While the flow is in the horizontal direction, in other embodiments, the flow is vertical.
The produced ozone can be used for many purposes, including, for example, the treatment
of water, waste water, air, etc., for the purpose of purification, disinfection and
elimination or neutralization of contaminants including bacteria.
[0029] Since the microtip pairs also operates well in air, arrays of microtips can also
be used to purify air as shown schematically in an air purifier of FIG. 9. An airflow
to be treated enters an enclosure 80 Conventional air filters such as a pre-dust filter
82 and a HEPA filter 84, which physically remove particles from the air flow stream
but are incapable of destroying pathogens (such as MRSA) or spores. Single or multiple
spaced arrays of microtip plasma devices 86 are in the enclosure 80 (which can be
a duct, for example in a hospital ventilation system, and are power by a power supply
90. The arrays 86 can be quite effective in destroying pathogens and can be replaceable
modules like the filters. The combined effect of the UV radiation emitted by the plasma
and the plasma itself will destroy contaminants and pathogens to a degree considerably
higher than that afforded by existing systems. Conventional dust and.
[0030] FIG. 10 illustrates a system in which an array 92 of microtip plasma devices formed
in a roll shape can be used to convert greenhouse or environmentally hazardous gases
into feedstock gases (or liquids) of commercial value. The device of FIG. 10 can be
powered and in an enclosure as illustrated in FIG. 9, but the array in a roll form
in FIG. 10 is shown alone for simplicity of illustration. One example application
is the conversion of CO
2 into ethanol or formic acid by mixing CO
2 with water vapor and exposing the mixture to the plasma array. Alternatively, CO
2 alone may be introduced to the input of the array and water vapor added downstream.
Although FIG. 10 shows a scroll-type configuration for the microplasma array, other
geometries (such as concentric cylinders) are also acceptable.
[0031] In FIG. 11, a schematic diagram showing a system of the invention that is for the
treatment of contaminated water, is presented which shows the treatment of contaminated
water by ultraviolet radiation produced by an array of microplasmas in an appropriate
gas such as one or more of the rare gases. Ultraviolet radiation of the proper wavelength
(normally UV-C) is known to be effective in destroying biological contaminants in
water. An array 100 of microtip plasma devices is enclosed in a UV transparent material
102 within a flow enclosure 104, such as a pipe. UV emissions generated 106 treat
the water flowing in the pipe 106. Additionally, gas flows can route produced ozone
through the water for treatment of the ozone with water.
[0032] The preferred embodiments have been shown to provide arrays of opposing microtips
encapsulated in dielectric, each pair of microtips capable of producing plasma in
a gas or mixture of gases lying immediately adjacent to the encapsulating dielectric
and in the vicinity of a microtip pair. Such an array of microplasmas can generate
ultraviolet (UV) or vacuum ultraviolet (VUV) radiation capable of, for example, destroying
pathogens in water and thus improving the purity of water in a municipal supply. Other
applications for the microplasmas generated by microtips of the invention include
the ozone production from oxygen or air, and the plasmachemical conversion of greenhouse
gases or atmospheric pollutants into industrial feedstock gases or liquids. Microtip
arrays of the invention are particularly well-suited for filters capable of destroying
pathogens (such as MRSA), spores, and other contaminants in the air supply for critical
environments, including surgical and patient rooms in hospitals and the homes of individuals
with compromised immune system.
[0033] While specific embodiments of the present invention have been shown and described,
it should be understood that other modifications, substitutions and alternatives are
apparent to one of ordinary skill in the art. Such modifications, substitutions and
alternatives can be made without departing from the scope of the invention, which
should be determined from the appended claims.
[0034] Various features of the invention are set forth in the appended claims.
1. An array (62, 64, 66, 86, 92, 100) of micro tip microplasma devices, comprising a
plurality of microtip microplasma devices,
wherein each microtip microplasma device comprises a first metal microtip (12a, 50a)
opposing a second metal microtip (12b, 50b) with a gap (16, 48) therebetween; and
wherein said first metal microtip comprises a portion of a first electrode (18a) and
said second metal microtip comprises a portion of a second electrode (18b),
characterized in that
said first and second metal microtips being encapsulated in metal oxide (14) that
electrically isolates and physically connects the first and second metal microtips;
and
said first and second electrodes and said metal oxide defining a mesh (30, 40) with
microscale openings (20) therein.
2. The array of claim 1, wherein said first and second metal electrodes (18a, 18b) are
encapsulated in metal oxide (14), and said first and second electrodes defining an
array of opposing metal microtips (12a, 12b, 50a, 50b) being separated by connecting
metal oxide.
3. The array of any of claims 1-2, wherein said first and second microtips comprise sharp
tips or rounded tips.
4. The array of claim 2, wherein said first and second electrodes comprise a single layer.
5. The array of claim 4, wherein said first and second electrodes and said metal oxide
comprise a monolithic, unitary structure.
6. The array of any of claims 1-2, wherein said first electrode and said second electrode
are interdigitated.
7. The array of any of claims 1-2, wherein said first and second electrodes comprise
aluminum and said oxide comprises aluminum oxide, or said first and second electrodes
comprise titanium and said oxide comprises titanium oxide.
8. The array of claim 2, wherein the first and second metal electrodes are thin enough
to make the array flexible.
9. A purification device, the device comprising a plurality of arrays of any of claim
1 arranged with respect to each to successively encounter a medium to be filtered.
10. The device of claim 9, wherein the plurality of arrays according to claim 1 are arranged
concentrically or in a flat stack.
11. A method of forming an array of microtip microplasma devices, the method comprising
steps of:
providing a metal mesh with an array of micro openings therein;
masking electrode areas of the metal mesh and leaving planned connecting metal oxide
areas of the metal mesh unmasked;
electrochemically etching the planned connecting metal oxide areas to convert the
planned connecting metal oxide areas to metal oxide that encapsulates opposing metal
microtips therein ; and
removing the mask; and
electrochemicall etchinig the electrode areas to encapsulate the electrode areas in
metal oxide.
12. The method of claim 11, further comprising the stesps of
electrochemically etching the planned connecting metal oxide areas to form opposing
metal microtips; and
encapsulating the opposing metal microtips in dielectric.
13. The method of claim 11, wherein said step of electrochemically etching the planned
connecting metal oxide area is continued at least until a sharp decline in etching
current indicates formation of the opposing metal microtips separated by the connecting
metal oxide areas.
1. Anordnung (62, 64, 66, 86, 92, 100) von Mikrospitzen-Mikroplasma-Vorrichtungen, die
eine Vielzahl von Mikrospitzen-Mikroplasma-Vorrichtungen umfasst,
wobei jede Mikrospitzen-Mikroplasma-Vorrichtung eine erste metallische Mikrospitze
(12a, 50a) gegenüber einer zweiten metallischen Mikrospitze (12b, 50b) mit einer Lücke
(16, 48) dazwischen umfasst und
wobei die erste metallische Mikrospitze einen Abschnitt einer ersten Elektrode (18a)
umfasst und die zweite metallische Mikrospitze einen Abschnitt einer zweiten Elektrode
(18b) umfasst, dadurch kennzeichnet, dass
die erste und die zweite metallische Mikrospitze in einem Metalloxid (14) verkapselt
sind, das die erste und zweite metallische Mikrospitze elektrisch isoliert und physisch
verbindet und wobei die erste und zweite Elektrode und das Metalloxid ein Gitter (30,
40) mit mikroskaligen Öffnungen (20) darin definieren.
2. Anordnung nach Anspruch 1, in der die ersten und zweiten metallischen Elektroden (18a,
18b) in Metalloxid (14) verkapselt sind und die ersten und zweiten Elektroden eine
Anordnung gegenüberliegender metallischer Mikrospitzen (12a, 12b, 50a, 50b) definieren,
die durch verbindendes Metalloxid getrennt sind.
3. Anordnung nach einem der Ansprüche 1-2, in der die ersten und die zweiten Mikrospitzen
scharfe Spitzen oder runde Spitzen umfassen.
4. Anordnung nach Anspruch 2, in der die ersten und die zweiten Elektroden eine einzelne
Schicht umfassen.
5. Anordnung nach Anspruch 4, in der die ersten und zweiten Elektroden und das Metalloxid
eine monolithische, einheitliche Struktur umfassen.
6. Anordnung nach einem der Ansprüche 1-2, in der die erste Elektrode und die zweite
Elektrode ineinandergreifend angeordnet sind.
7. Anordnung nach einem der Ansprüche 1-2, in der die ersten und zweiten Elektroden Aluminium
umfassen und das Oxid Aluminiumoxid aufweist, oder die ersten und zweiten Elektroden
Titan umfassen und das Oxid Titanoxid umfasst.
8. Anordnung nach Anspruch 2, in der die ersten und zweiten metallischen Elektroden dünn
genug sind, um die Anordnung biegsam zu machen.
9. Reinigungsgerät, wobei das Gerät eine Vielzahl von Anordnungen nach Anspruch 1 umfasst,
die in Bezug zueinander nacheinander angeordnet sind, um einem zu filternden Medium
zu begegnen.
10. Gerät nach Anspruch 9, bei dem die Vielzahl von Anordnungen nach Anspruch 1 konzentrisch
oder in einem flachen Stapel angeordnet sind.
11. Verfahren zum Bilden einer Anordnung von Mikrospitzen-Mikroplasma-Vorrichtungen, wobei
das Verfahren die Schritte umfasst von:
Bereitstellen eines Metallgitters mit einer Anordnung von Mikro-Öffnungen darin, Maskieren
von Elektrodenbereichen des Metallgitters und unmaskiert Zurücklassen von geplanten
Metalloxid-Bereichen des Metallgitters,
elektrochemisches Ätzen der geplanten verbindenden Metalloxid-Bereiche, um die geplanten
verbindenden Metalloxid-Bereiche zu Metalloxid umzusetzen, das die gegenüberliegenden
metallischen Mikrospitzen darin verkapselt und Entfernen der Maske und
elektrochemisches Ätzen der Elektrodenbereiche, um die Elektrodenbereiche in Metalloxid
zu verkapseln.
12. Verfahren nach Anspruch 11, das weiter die Schritte des elektrochemischen Ätzens geplanter
verbindender Metalloxid-Bereiche umfasst, um gegenüberliegende metallische Mikrospitzen
zu bilden und Verkapseln der gegenüberliegenden metallischen Mikrospitzen in Dielektrikum.
13. Verfahren nach Anspruch 11, bei dem der Schritt des elektrochemischen Ätzens der geplanten
verbindenden Metalloxid-Bereiche wenigstens fortgesetzt wird, bis ein scharfer Abfall
der Ätzspannung die Bildung einander gegenüberliegender metallischer Mikrospitzen
anzeigt, die durch die verbindenden Metalloxid-Bereiche getrennt sind.
1. Réseau (62, 64, 66, 86, 92, 100) de dispositifs à microplasma à micropointes, comprenant
une pluralité de dispositifs à microplasma à micropointes, dans lequel chaque dispositif
à microplasma à micropointes comprend une
première micropointe métallique (12a, 50a) opposée à une seconde micropointe métallique
(12b, 50b), les deux étant séparées avec un espace (16, 48); et dans lequel ladite
première micropointe métallique comprend une partie d'une première électrode (18a)
et ladite seconde micropointe métallique comprend une partie d'une seconde électrode
(18b), caractérisé en ce que lesdites première et
seconde micropointes métalliques étant encapsulées dans un oxyde métallique (14) qui
isole électriquement et connecte physiquement les première et
seconde micropointes métalliques; et lesdites première et seconde électrodes et ledit
oxyde métallique définissant un treillis (30, 40) comportant des ouvertures à l'échelle
micrométrique (20).
2. Réseau selon la revendication 1, dans lequel lesdites première et seconde électrodes
métalliques (18a, 18b) sont encapsulées dans un oxyde métallique (14), et lesdites
première et secondes électrodes définissant un réseau de micropointes métalliques
opposées (12a, 12b, 50a, 50b) sont séparées par l'oxyde de métal de liaison.
3. Réseau selon l'une quelconque des revendications 1 et 2, dans lequel lesdites première
et seconde micropointes comprennent des pointes acérées ou des pointes arrondies.
4. Réseau selon la revendication 2, dans lequel lesdites première et seconde électrodes
comprennent une seule couche.
5. Réseau selon la revendication 4, dans lequel lesdites première et seconde électrodes
et ledit oxyde métallique comprennent une structure monolithique unitaire.
6. Réseau selon l'une quelconque des revendications 1 à 2, dans lequel lesdites première
et seconde électrodes sont entrecroisées.
7. Réseau selon l'une quelconque des revendications 1 à 2, dans lequel lesdites première
et seconde électrodes comprennent de l'aluminium et ledit oxyde comprend de l'oxyde
d'aluminium, ou les première et seconde électrodes comprennent du titane et ledit
oxyde comprend de l'oxyde de titane.
8. Réseau selon la revendication 2, dans lequel les première et seconde électrodes métalliques
sont suffisamment minces pour rendre le réseau flexible.
9. Dispositif de purification, le dispositif comprenant une pluralité de réseaux selon
la revendication 1, disposés de manière à rencontrer successivement un milieu à filtrer.
10. Dispositif selon la revendication 9, dans lequel la pluralité de réseaux selon la
revendication 1, sont disposés concentriquement ou en une pile plate.
11. Procédé de formation d'un réseau de dispositifs à micro-plasma à micropointes, le
procédé comprenant les étapes consistant à:
fournir un treillis métallique comportant une série de micro-ouvertures;
masquer les zones d'électrode du treillis métallique et laisser exposées les zones
d'oxyde métallique de liaison prévues du treillis métallique;
décaper électrochimiquement les zones d'oxyde métallique de liaison prévues pour convertir
les zones d'oxyde métallique de liaison prévues en un oxyde métallique qui encapsule
des micropointes métalliques opposées dans celles-ci;
et retirer le masque ; et
décaper électrochimiquement les zones d'électrode pour encapsuler les zones d'électrode
dans l'oxyde de métal,
12. Procédé selon la revendication 11, comprenant en outre les étapes consistant à décaper
électrochimiquement les zones d'oxyde métallique de liaison prévues pour former des
micropointes métalliques opposées; et encapsuler les micropointes métalliques opposées
dans un diélectrique.
13. Procédé selon la revendication 11, dans lequel l'étape consistant à décaper électrochimiquement
la zone d'oxyde métallique de liaison prévue jusqu'à ce qu'au moins une forte baisse
du courant de décapage indique la formation de micropointes métalliques opposées et
séparées par les zones d'oxyde métallique de liaison.